In conventional boat lifts, a boat or other type of watercraft is accommodated on a platform which is typically raised and lowered by a winch and cable mechanism. A wide variety of such lifts are known. However, virtually all exhibit one or more of a number of disadvantages.
The lift platform is usually raised by a motor or hand crank. To return the vessel to the water, the platform is lowered with the assistance of gravity. Most known boat lifts employ either a gear reduction or a separate brake mechanism to slow the descent of the platform. Such mechanisms contribute significantly to the complexity and expense of the boat lift.
Additionally, many standard cable-operated lift platforms experience problems with buoyancy. In order to properly lower the boat into the water, the hull of the vessel must be partially submerged. Most boat lift platforms employ structural components (e.g. cradle beams, bunk boards, etc.) that are composed of buoyant materials such as wood or lightweight aluminum. Consequently, as the lift platform is lowered by gravity it tends to float on the water. This can prevent the hull of the watercraft from being properly submerged. Moreover, when the platform suddenly engages the water and floats, the cables may continue to unwind from the spool of the winch. This can cause the cables to unravel and tangle. Operation of the boat lift may be disrupted and costly, time consuming repairs may be required.
Standard cable driven boat lifts also employ a fairly intricate lifting mechanism. Typically, four sets of cables, pulleys and motors are required to raise and lower the lift platform.